In recent years endovascular implantable devices have been developed for treatment of aortic aneurysms. These devices are delivered to the treatment site through the vascular system of the patient rather than by open surgery. The devices include a tubular or cylindrical framework or scaffolding of one or more stents to which is secured a tubular shape of graft material such as woven Dacron, polyester polytetrafluoroethylene or the like. The devices are initially reduced to a small diameter, placed into the leading or proximal end of a catheter delivery system whereafter the delivery system is inserted into the vascular system of the patient such as through a femoral incision. The leading end of the delivery system is manoeuvred to the treatment site over a previously positioned guide wire. Through manipulation of a control system that extends to the proximal end of the catheter from the distal end of the system outside the patient, the implantable device is deployed by holding the device at its location and withdrawing a surrounding sheath. The implantable device or stent graft can then self expand or be expanded through the use of a balloon which is introduced with a stent graft introduction device. The stent graft becomes anchored into position in healthy wall tissue of the aorta, by barbs for example. The delivery system is then removed leaving the inflatable device in position to reverse an aneurysm in the aorta in a manner that channels all blood flow through the stent graft so that no blood flow enters the aneurysm. As a result, not only does the aneurysm no longer continue to grow and possibly rupture but the aneurysm actually begins to shrink and commonly disappears entirely.
For treatment of thoracic aortic aneurysms in particular it is necessary to introduce the implantable device high up in the aorta and in a region of the aorta which is curved and where there can be strong blood flow.
In the thoracic aorta there are major branch vessels, the brachiocephalic, the left carotid and the left subclavian. For treatment of an aneurysm in the region of the thoracic arch provision must be made for blood supply to continue to these arteries. For this purpose fenestrations are provided into the wall of a stent graft in that region. Access is generally obtained to these fenestrations, to deploy side arms into the stent graft, via the left or right brachial arteries or less commonly via the left or right carotid arteries. Once into the thoracic arch via such an artery the fenestration in the stent graft must be catheterised. To simplify this, it is desirable to have some working space in the outer side of the thoracic arch which is the region that the branch vessels enter the arch.
It is the object of this invention to provide an arrangement of stent graft to overcome the above problem or to at least provide the practitioner with a useful alternative.
Throughout this specification the term distal with respect to a portion of the aorta, a deployment device or a prosthesis such as a stent graft is intended to mean the end of the aorta, deployment device or prosthesis such as a stent graft further away in the direction of blood flow from the heart and the term proximal is intended to mean the portion of the aorta, deployment device or end of the prosthesis nearer to the heart. For other lumens within the human or animal body the terms caudal and cranial respectively should be understood.
Throughout this discussion the term “stent graft” is intended to mean a device which has a tubular body of biocompatible graft material and at least one stent fastened to the tubular body to define a lumen through the stent graft. The stent graft may be bifurcated and have fenestrations, side arms or the like. Other arrangements of stent grafts are also within the scope of the invention.